In a storage subsystem using multiple storage devices and operated in a RAID (Redundant Array of Independent (Inexpensive) Disks) configuration, a structure is adopted where two or more control modules are installed to constantly realize redundancy. Further, as taught in Patent Literature 1, cooling fans are provided in the configuration to discharge the heat generated from devices disposed inside the storage subsystem. Similar to the control module, multiple cooling fans are installed to realize redundancy. It is preferable that the output of the cooling fans are changed according to the heat quantity.
The technique taught in Patent Literature 1 teaches a configuration where a hardware fan control unit for controlling the cooling fans via hardware is provided in a PLD (Programmable Logical Device), and the control of the cooling fans is performed until cooling fan control becomes possible using firmware. At this time, controller modules notify each other of the status of installation of modules, and all the cooling fans are controlled collectively by a controller module having the smallest ID of the IDs indicated by a combination of signals showing the status of installation thereof.